Automatic shift control system for automatic transmission

ABSTRACT

A shift signal control system having an engine torque responsive signal generator, a vehicle speed responsive signal generator, and a plurality of discriminating circuits generating an output signal when one of these two signals or the relation between these two signals satisfies a predetermined condition. At least one of the discriminating circuits is disconnectably connected with an OR circuit through a switch while the remaining discriminating circuits are directly connected with the OR circuit so that an output signal is delivered from the OR circuit for carrying out ratio changes in response to the application of at least one of the output signals from the discriminating circuits.

United States Patent Ito et al.

451 Aug. 1,1972

[54] AUTOMATIC SHIFT CONTROL SYSTEM FOR AUTOMATIC TRANSMISSION [72] Inventors: Shin Ito, 10, Toyotacho; Seitoku Kubo, 8, Toyotacho, both of Toyota, Japan [22] Filed: March 20, 1970 [21] Appl. N0.: 21,351

[30] Foreign Application Priority Data Jan. 4, 1969 Japan ..44/25030 [52] US. Cl ..74/866, 74/869 [51] Int. Cl. ..B60k 21/00 [58] Field of Search ..74/866 56] References Cited UNITED STATES PATENTS 3,448,640 6/1969 Nelson ..74/866 POM Ex? SOURCE SH/F 7 S/G/VAL CONTROL 3,267,762 8/1966 Reval ..74/866 X 3,301,085 1 H1967 De Castelet ..74/866 3,433,101 3/1969 Scholl et al. ..74/866 Primary ExaminerArthur F. McKeon Att0rney--Cushman, Darby & Cushman 5 7 ABSTRACT A shift signal control system having an engine torque responsive signal generator, a vehicle speed responsive signal generator, and a plurality of discriminating circuits generating an output signal when one of these two signals or the relation between these two signals satisfies a predetermined condition. At least one of the discriminating circuits is disconnectably connected with an OR circuit through a switch while the remaining discriminating circuits are directly connected with the OR circuit so that an output signal is delivered from the OR circuit for carrying out ratio changes in response to the application of at least one of the output signals from the discriminating circuits.

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AUTOMATIC SIIIFI CONTROL SYSTEM FOR AUTOMATIC TRANSMISSION This invention is an improvement on the subject matter set forth in the copending Wakamatsu et a1. application, Ser. No. 874,934 filed Nov. 7, 1969, and relates to automatic transmissions for automotive vehicles and the like, and more particularly to an automatic shift control system comprising a combination of electrical and fluid control means for use in an automatic transmission.

Automatic transmissions generally employed heretofore generally relied on fluid pressure for carrying out all the complex vehicle functions including shifting. Thus, the signal detection system in such an automatic transmission is generally complex in structure and the detected signals in the form of a fluid differential is subject to errors and therefore generally so inaccurate that accurate control is not possible. Further, the hydraulic actuating circuit in such a transmission is also so complex in structure that it is not easy to improve it.

The conventional automatic transmission involved various disadvantages due to the fact that only one set of shift points or only one shift pattern existed for a shift between low and high gear. More precisely, a shift pattern suitable for normal driving on a level road was commonly provided in the conventional automatic transmission and it was thus impossible to select a suitable automatic shift pattern among automatic shift patterns depending on the driving condition of the vehicle or at the discretion of the driver. Suppose, for example, that a vehicle equipped with a conventional three-forward speed automatic transmission enters a mountainous area while driving in the third gear of a relatively low speed range and starts to run up an incline. Since, in this case, the running resistance is increased 'and the accelerating force gradually decreases, the

driver normally kicks down the accelerator pedal into downshift to second gear. Subsequently, however the release of the force imparted to the accelerator pedal at a curve or the like immediately causes an upshift to third gear resulting in an abrupt and undesirable reduction in accelerating power. In order to avoid this, the vehicle should continue to run in second gear without being upshifted into third gear. It is thus impossible under these circumstances with the conventional transmission to carry out a suitable shifting pattern by adjusting the amount of depression of the accelerator pedal.

It is therefore an object of the, present invention to provide an electrically controlled shift signal control system for an automatic transmission in which a plurality of automatic shift patterns are provided so that a suitable automatic shift pattern can be selected in accordance with different driving conditions to carry out an automatic shift best suited to any particular driving condition.

Another object of the present invention is to provide a shift signal control system comprising means for generating an engine torque responsive signal, means for generating a vehicle speed responsive signal, a plurality of discriminating circuits generating an output signal when one of these two signals generated by said signal generating means or the relation between said two signals satisfies a predetermined condition, switch means connected with the output of at least one of said discriminating circuits for permitting or interrupting the delivery of the output signal from said discriminating circuit, and an OR circuit connected with at least one of said discriminating circuits through said switch means and with the remainder of said discriminating circuits directly so as to carry out ratio changes when at least one of the output signals from said discriminating circuits is applied thereto.

Thus, according to the present invention, a suitable shift pattern among a plurality of shift patterns can be freely selected depending on the driving condition of the vehicle by virtue of the provision of a plurality of discriminating circuits and a switching means as described above. By this arrangement, a suitable shift point (Iine)'can be selected depending on the driving condition of the vehicle or on the preference of the driver by merely suitably turning and switching means on or off. Thus, the automatic shift control system according to the present invention is advanced compared with prior art automatic transmissions primarily in that it has a variety of automatic shift points.

The above and other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of an automatic transmission embodying the present invention;

FIG. 2 is a schematic sectional view of a transmission unit in the automatic transmission of the present invention;

FIG. 3 is an enlarged sectional view taken on the line A-A in FIG. 2 with parts cut away to show in detail the relation between an idler gear not shown in FIG. 2 and the sun gear and planet pinion;

FIGS. 4 through 10 are diagrammatic views illustrating the operating state at various positions of a hydraulic actuating circuit in the automatic transmission according to the present invention, wherein FIG. 4 illustrates the operating state at the N position, FIG. 5 the operating state at the D position-1st speed, FIG. 6 the operating state at the D position-2nd speed, FIG. 7 the operating state at the D position-3rd speed, FIG. 8 the operating state at the 2 position-2nd speed, FIG. 9 the operating state at the L position, and FIG. 10 the operating state at the R position;

FIG. 11 is a chart showing the variation in the line pressure PL controlled by the hydraulic actuating circuit relative to the r.p.m. of the output shaft;

FIG. 12 is a block diagram of a shift signal control system preferably used in the automatic transmission of the present invention;

FIGS. 13a and 13b :are a side elevational view and a front elevational view,respectively, of an r.p.m. detector preferably used in the shift signal control system;

FIG. 14 is a block diagram showing the structure of a digital-analog converter preferably used in the shift signal control system;

FIGS. 15a, 15b and are graphic illustrations of the operating voltage waveforms appearing in the digital-analog converter shown in FIG. 14;

FIG. 16 is a circuit diagram showing the structure of a throttle position responsive circuit employed in the shift signal control system;

FIG. 17 is a circuit diagram showing the structure of a discriminating circuit and an associated feedback circuit employed in the shift signal control system;

FIG. 18 is a chart showing the relation between a signal representing the output shaft rpm. and a signal representing the throttle position for determining the shift regions according to the present invention; and

FIG. 19 is a shift diagram showing one example of the shift regions according to the present invention.

Referring to FIG. 1, the automatic transmission embodying the present invention including a source of electrical power supply 500, a shift signal control system 501, a switch 95 connecting the shift signal control system 501 with the electrical power source 500, a hydraulic actuating system 502 and a transmission ,unit 503. These components are described in detail hereunder.

STRUCTURE OF TRANSMISSION A torque converter automatic transmission having three forward speeds and one reverse speed as shown in FIG. 2 is taken as a typical example of an automatic transmission. In FIG. 2, the structure of the fluid controlled automatic transmission is schematically shown.

A torque converter unit includes a pump impeller 2 directly connected to the crankshaft 1 of an engine. The power developed by the engine is transmitted from the pump impeller 2 to a turbine impeller 3 through an hydraulic fluid, and the fluid is returned to the pump impeller 2 guided by a stator 4. A rotational force can be continuously derived from a turbine shaft 5 by the flow of the fluid. This rotational force is transmitted from the turbine shaft 5 to a gear unit disposedat the output side of the torque converter unit. As is commonly known, multiple disc clutch means 6 and 7 and brake band means 21 and 22 are automatically controlled by a fluid pressure supplied from the associated servo means as required and these cooperate with a planetary gear mechanism to provide three forward speeds and one reverse speed.

The structure of the gear unit disposed at the output side of the torque converter unit will now be described. The turbine impeller 3 is connected to the turbine shaft 5 which acts as the power input shaft of the planetary gear mechanism. The turbine shaft 5 is splined to a drum 24 for unitary rotation therewith. Disposed within the drum 24 is a multiple disc clutch 6 (hereinafter to be referred to as a front clutch) which is I engaged by means of a piston 25 actuated by fluid pressure and which is released by means of back-up springs. The drive plates of the front clutch 6 are externally splined to engage the internally splined portion of the drum 24, and the clutch discs are internally splined to engage the externally splined portion of a hub 26 so as to be locked against free rotation. The hub 26 is internally splined to engage the externally splined portion of an intermediate shaft 8. The clutch discs of a multiple disc clutch 7 (hereinafter to be referred to as a rear clutch) are internally splined to engage the externally splined portion of the front clutch drum 24 as shown so as to be locked against free rotation. Thus, the clutch discs of the rear clutch 7 rotate in unison with the front clutch drum 24. The driven plates of the rear clutch 7 are externally splined to engage with the internally splined portion of a clutch drum 27 of the rear clutch 7.

The rear clutch 7 is engaged by means of a fluid pressure actuated piston 28 and it is disengaged when the fluid pressure applied to piston 28 is released.

The intermediate shaft 8 which is splined to the hub 26 of the front clutch 6 is connected at its rear end to an input sun gear 9. The rear clutch drum 27 is fixed to a reverse sun gear 10 by a suitable locking means. The input sun gear 9 meshes with each gear 12 of a plurality of, for example, two or three planet pinions 11. The reverse sun gear 10 meshes with idler gears 15 (shown in FIG. 3) which are each rotatably mounted on a pin 14 fixed at one end to a carrier 13, and the idler gears 15 in turn meshes with gears 16 of the planet pinions 1 l.

The rearmost gear 17 of each planet pinion 11 meshes with a gear 19 mounted at the front end of an output shaft 18 of the transmission. The planet pinions 11 having the gears 16, 12 and 17 and the idler gears or pinions 15 are carried by the carrier 13 by means of pinion pins 20 and 14, respectively. A brake band 21 (hereinafter to be referred to as a rear brake band) encircles the carrier 13 for applying a brake to the latter, and thus the carrier 13 can be fixed against rotation and allowed to freely rotate by fastening and releasing the rear brake band 21 respectively. Similarly, a brake band 22 (hereinafter to be referred to as a front brake band) encircles the rear clutch drum 27 so that the rear clutch drum 27, and hence the reverse sun gear 10 can be fixed against rotation and allowed to freely rotate by fastening or releasing the front brake band 22 respectively. A one-way clutch 23 associated with the carrier 13 functions in a manner similar to the rear brake band 21 in low gear as set forth hereunder.

With the above structure, three forward speeds and one reverse speed can be obtained by selectively actuating the elements described above in a manner as follows:

First speed The front clutch 6 and the rear brake band 21 are actuated. (However, when the transmission is driven from the engine, the rear brake band 21 may not be actuated, since the one-way clutch 23 is actuated to give the same result as that obtained with the actuation of the rear brake band 21. In this case, however, no driving force is transmitted from the output shaft 18.) With the front clutch 6 and the rear brake band 21 so actuated, the rotation of the turbine shaft 5 is directly transmitted to the input sun gear 9 through the front clutch 6. Due to the fact that the carrier 13 is locked against rotation by the rear brake band 21, the pinion pins 20 are also held stationary and the rotation of the turbine shaft 5 is transmitted from the gear 9 to the gears 12, thence through the gears 17 to the gear 19 on the output shaft 18 in a speed reducing relation similar to that of an ordinary gear train, thereby providing the first speed.

Second speed The front clutch 6 is kept actuated and the front brake band 22 is actuated while releasing the rear brake band 21. Thus, the input sun gear 9 is rotated in unison with the turbine shaft 5, but the rear clutch drum 27, hence the reverse sun gear 10 is locked against rotation by the front brake band 22. In this state, the rotation of the turbine shaft 5 is directly transmitted to the input sun gear 9, and the sun gear 9 urges the pinions 11 to rotate in a direction (counterclockwise) opposite to the direction of rotation (clockwise) of the turbine shaft 5. The planet pinions 11 rotating in this direction try to rotate the idler gears 15 clockwise through the gears 16. However, due to the fact that the gear meshing with the gears is locked against rotation, the pinion pin 14 revolves clockwise around the gear 10. This revolving motion is imparted to the rotation of the input sun gear 9 and the gear 19 carried by the output shaft 18 which gears are coaxial with and rotate in the same direction as the turbine shaft 5. Since the number of teeth of the gear 12 is selected to be greater than the number of teeth of the gear 17, the number of revolutions of the intermediate shaft 8 is greater than that of the output shaft 18. In other words, the output shaft 18 is rotated at a reduced speed or second speed.

Third speed The third speed can be obtained by engaging both the front and rear clutches 6 and 7. The input sun gear 9 and the reverse sun gear 10 are rotated in unison and the whole planetary gear system is unitarily rotated so that the output shaft 18 is rotated at the same speed of rotation as the turbine shaft 5.

Reverse When reversing, the rear clutch 7 and the rear brake band 21 are actuated. The carrier 13, hence the pinion pins 14 and are thereby locked against revolution, and the rotation of the turbine shaft 5 is transmitted through the rear clutch 7 to the reverse sun gear 10, thence through the pinions 15 and 17 to the gear 19 mounted on the output shaft 18 so that the output shaft 18 is rotated in the reverse direction.

HYDRAULIC ACTUATING SYSTEM The arrangement of a hydraulic actuating system for use in an automatic transmission mechanism according to the present invention is diagrammatically shown in FIGS. 4 through 10. Briefly, the hydraulic actuating system comprises a fluid pressure source 100 and a hydraulic actuating circuit 110. The hydraulic actuating circuit 110 includes a manual valve 120, a 1-2 shift means 130, a 2-3 shift means 135, a check valve 140 and fluid passages. The fluid pressure source 100 includes an oil pump 101, an oil strainer 102, a pressure regulator valve 105, a check valve 103, an oil cooler 104 and fluid passages. The fluid pressure source 100 functions to supply fluid under pressure to the torque converter, to the gears for lubricating same and to the hydraulic actuating circuit 110.

The manual valve 120 is connected with a shift lever (now shown) disposed adjacent to the drivers seat and takes one of the P, R, N, D, 2 and L positions. When now the manual valve 120 takes the N position, a fluid passage 121 is closed and valve chambers 122 and 123 are exhausted as seen in FIG. 4. At the D position of the manual valve 120, the fluid passage 121 communicates with fluid passages 124, 125 and 126 as seen in FIG. 5. The fluid passage 124 leads directly to a front clutch servo chamber 6a, and the fluid passage 125 leads to the apply side 22a of a servo for the front brake band 22 through the 1-2 shift means 130, while the fluid passage 126 leads to a rear clutch servo chamber 7a and to the release side 22b of the servo for the front brake band 22 through the 2-3 shift means 135 and the check valve 140. The 1-2 shift means 130 includes a 1- 2 shift valve element 131 and a solenoid 132. One end (or the right-hand end as viewed in the drawing) of the valve element 131 is abutted by a moving core 133 of the solenoid 132. When no current is supplied to the solenoid 132, the valve element 131 is urged to its rightward position by a spring 131a which engages the other or left-hand end of the valve element 131 so that the fluid passage communicates with a fluid passage 134 to supply fluid to the apply side 22a of the servo for the front brake band 22 to apply the front brake band 22. When current is supplied to the solenoid 132, the moving core 133 urges the valve element 131 to the leftward position by being actuated by the electromagnetic force of the solenoid 132 so that the communication between the fluid passages 125 and 134 is interrupted and the fluid passage 134 communicates with a pressure discharge port 134a to release the front brake band 22. Similarly, the 2-3 shift means 135 includes a 2-3 shift valve element 136 and a solenoid 137. One end (or the right-hand end as viewed in the drawing) of the valve element 136 is engaged by a moving core 138 of the solenoid 137. When no current is supplied to the solenoid 137, the valve element 136 is urged to its rightward position by a spring 136a engaging the other or left-hand end of the valve element 136 so that the fluid passage 126 communicates with a fluid passage 139 to force a check ball element 141 of the check valve towards the fluid passage 128 to block the fluid passage 128. As a result, the fluid passage 139 communicates with fluid passage 142 to supply fluid to the rear clutch servo chamber 7a and to the release side 22b of the servo for the front brake band 22 so as to engage the rear clutch 7 and release the front brake band 22. When current is supplied to the solenoid 137, the valve element 136 is urged leftward so that the communication between the fluid passages 126 and 139 is interrupted and the fluid passage 139 communicates with a pressure discharge port 139a to be exhausted.

In the first speed at the drive range position or D position 1st speed shown in FIG. 5, both the solenoids 132 and 137 are energized and the front clutch 6 is solely engaged by the fluid supplied to the front clutch servo chamber 6a through the fluid passage 124. Accordingly, when the transmission is driven from the engine, the one-way clutch 23 is actuated to lock the carrier 13 against rotation so that the first speed can be obtained. In this case, however, no driving force can be transmitted from the output shaft since a freewheeling action takes place.

In the second speed at the drive range position or D position2nd speed shown in FIG. 6, the fluid passage 124 leading to the front clutch servo chamber 6a is kept pressurized and the solenoid 132 for the 1-2 shift valve element 131 is de-energized with the result that the fluid passage 125 communicates with fluid passage 134 to supply fluid to the apply side 22a of the servo for the front brake band 22 to apply the front brake band 22. Thus, the second speed can be obtained.

In the third speed at the drive range position or D position-3rd speed shown in FIG. 7, the solenoid 137 for the 2-3 shift valve element 136 is de-energized in addition to the previous de-energization of the solenoid 132 in the D position-2nd speed with the result that the fluid passage 126 communicates with the fluid passage 139 to supply fluid to the rear clutch servo chamber 7a to engage the rear clutch 7 while releasing the front brake band 22. Thus, the third speed can be attained.

When the manual valve 120 is urged to the 2 position shown in FIG. 8, the fluid passage 126 leading to the 2- 3 shift means 135 is exhausted and the fluid passages 124 and 125 communicate solely with the fluid pressure source 100. Accordingly, it is impossible to obtain the third speed, regardless of the de-energization of the solenoid 137 for the 2-3 shift valve element 136 and the first and second speeds can be obtained depending on the venergization and de-energization of the solenoid 132 for the 1-2 shift valve element 131.

When the manual valve 120 is urged to the L position shown in FIG. 9, the fluid passages 125 and 126 are exhausted and the fluid passages 124 and 127 communicate with the fluid pressure source 100. As a result, fluid is supplied to the front clutch servo chamber 6a and to the apply side 21a of a servo for the rear brake band 21 to engage the front clutch 6 and apply the rear brake band 21. Thus, the first speed can be obtained. The first speed in this case differs from the first speed in the D position in that the rear brake band 21 is applied to allow for the transmission of the driving force from the output shaft to the engine thereby permitting engine braking.

When the manual valve 120 is moved to the R position shown in FIG. 10, the fluid passages 124, 125 and 126 are exhausted and the fluid passages 127 and 128 communicate with the fluid pressure source 100. As a result, fluid is supplied to the rear clutch servo chamber 7a and to the apply side of the servo for the rear brake band 21 to engage the rear clutch 7 and apply the rear brake band 21. Thus, the reverse drive condition for the vehicle can be obtained.

It will be understood from the foregoing description thatthe hydraulic actuating system in the present invention is featured by the fact that it comprises a novel combination of a hydraulic circuit arrangement and biasing means in the form of springs 131a and 136a for biasing the 1-2 shift valve element 131 and the 2-3 shift valve element 136 to the upshift position in response to de-energization of the respective solenoids 132 and 137. The circuit arrangement of the hydraulic actuating system is such that, in the first, second and third speed at the D position of the manual valve 120, fluid pressure from the fluid pressure source 100 is supplied to the front clutch servo chamber 6a through the fluid passage 124,.to the apply side 22a of the servo for the front brake band 22 through the fluid passage 125 and the 1-2 shift means 130, and to the rear clutch servo chamber 7a for the rear clutch 7 and to the release side 22b of the servo for the front brake band 22 through the fluid passage 126 and the 2-3 shift means 135, respectively.

In the 2 position of the manual valve 120, the fluid passage 126 leading to the 2-3 shift means 135 is exhausted and fluid passages 124 and 125 both communicate with the fluid pressure source 100, which in the L position of the manual valve 120, the fluid passage 125 leading to the 1-2 shift means 130 is further exhausted and the fluid passage 124 leading to the front clutch servo chamber 6a for the front clutch 6 and the fluid passage 127 leading to the apply side 21a of the servo for the rear brake band 21 communicate with the fluid pressure source 100. By virtue of the above combination, even when the power supplied from the electrical power source to the shift signal control system is interrupted, the manual valve 120 may be urged to the L position for obtaining the first speed, to the 2 position for obtaining the second speed and to the D position for obtaining the third speed. Such a hydraulic circuit arrangement is quite advantageous in that, when trouble occurs in the shift signal control system which controls the supply of electrical signals to the solenoids or when the driver wishes a sporty drive with a variety of speed changes compared with those carried out on the basis of the shift points set for the electrical control system, the driver may turn off the switch connecting the voltage source with the shift signal control system to cut off the supply of power to the shift signal control system thereby rendering the shift signal control system inoperative and may then shift the shift lever to one of the L, 2 and D positions so as to select the speed ratio desired by the driver. In other words, the switch may be turned on and off to select either a fully automatic or a manual drive as desired.

A second feature of the present invention resides in the fact that the freewheeling drive appears in the D position-1st speed so as to ensure protection against any erratic first speed signal that may be supplied from the shift signal control system under high speed driving.

A third feature of the present invention resides in the fact that the solenoids 132 and 137 are in the de-energized state during running of the vehicle in the third speed gear. Therefore, it is unnecessary to consider any electrical power consumption due to operation of the solenoids as well as the undersirable generation of heat resulting in a temperature rise due to the current supplied to the solenoids.

Fluid pressure supplied to the servos is controlled by the pressure regulator valve 105. The pressure regulator valve includes ,a valve spool 105a which is engaged at one or upper end by a spring 106. In the R position of the manual valve 120, fluid pressure is supplied through a fluid passage 128 to a valve chamber 107 surrounding the upper portion of the valve spool 105a. Spaced valve chambers 108 and 109 surround the lower portion of the valve spool 105a so that fluid pressure is supplied from thev oil pump 101 to the chamber 108 and fluid pressure is supplied to the chamber 109 through a fluid passage 134b. In the D or 2 position of the manual valve 120, fluid pressure is supplied to the fluid passage 125 leading to the 1-2 shift means 130. Then, when the 1-2 shift solenoid 132 is deenergized, the valve element 131 is urged to the upshift position to establish communication between the fluid passages 125 and 134 'so that fluid pressure is supplied to the chamber 109 through the fluid passage 13412. On the other hand, the chamber 107 is exhausted in all the gear positions, with the exception of the reverse position. Thus, a constant low fluid pressure P which is determined by the spring pressure of the spring 106 and fluid pressures in the chambers 108 and 109, is produced by the pressure regulator valve 105.

When the manual valve is in the D or 2 position and the 1-2 shift valve element 131 is urged to the downshift position (corresponding to the first speed) by the operation of the solenoid 132 or when the manual valve 120 is in the L position, the chamber 109 of the pressure regulator valve 105 is exhausted and a constant fluid pressure P which is determined by the spring pressure of the spring 106 and fluid pressure in the chamber 108, is produced by the pressure regulator valve 105.

In the R position of the manual valve 120, fluid pressure is supplied to the chamber 107 of the pressure regulator valve 105 through the fluid passage 128. Accordingly, a constant high fluid pressure P which is determined by the spring pressure of the spring 106 and fluid pressures in the chambers 107 and 108, is produced by the pressure regulator valve 105.

It will be understood from the above description that the fluid passage 134 leading out from the l-2 shift means 130 is connected to the pressure reducing chamber 109 of the pressure regulator valve 105 so that the fluid pressure produced by the pressure regulator valve 105 is reduced when the 1-2 shift valve element 131 is shifted to the high gear position.

FIG. 11 shows the variation in the fluid pressure or line pressure P produced by the pressure regulator valve 105 relative to the number of revolutions of the output shaft 18, hence the vehicle speed. As will be seen from FIG. 11, a step-down from the constant fluid pressure P to the constant low fluid pressure P occurs in the 2 or D position of the manual valve 120 when the number of revolutions of the output shaft 18, hence the vehicle speed is increased and the speed ratio is changed from the first to the second speed. Generally, the 1-2 shift point and 2-1 shift points are variable depending on an engine torque responsive signal. Thus, the step-down point from the constant fluid pressure P to the constant low fluid pressure P varies as shown depending on the engine torque responsive signal.

By virtue of the capability of obtaining the control pressure characterized in the manner described in detail above, a line pressure taking into consideration the torque multiplying action of the torque converter can be supplied to the servo chambers for the clutches and brake bands so as to provide a sufficient large engaging force in the low speed range, while a constant low line pressure can be supplied to the servo chambers to prevent power losses including any loss which may occur in the oil pump and other elements in the high speed range, since the torque multiplying action of the torque converter is lost in the high speed range due to the fact that the torque converter also substantially acts as a hydraulic coupling.

According to the present invention, further, the shift valve means provided for the sake of shift control acts also as a means for varying the fluid pressure control action of the pressure regulator valve 105. This eliminates the need for providing a valve (such as the so-called compensator valve or throttle relay valve) employed in prior art automatic transmissions for varying the fluid pressure control action of the pressure regulator valve and remarkably simplifies the structure of the hydraulic circuit.

It will be seen from the above description that the method of controlling the fluid pressure in the hydraulic actuating circuit employed in the automatic transmission according to the present invention has various notable features and advantages. However, the method described above is not the subject matter of the present invention as it has already been applied for a patent in a copending patent application.

It will be understood that the 1-2 shift means 130 and the 2-3 shift means 135 are operated to vary the pressure regulating action of the pressure regulator valve 105 and to carry out the automatic speed changing operation, and this is accomplished by selectively energizing and de-energizing the solenoids 132 and 137.

The selective energization and de-energization of the solenoids 132 and 137 are carried out under the control of a unique shift signal control system. The shift signal control system is the essential feature of the present invention and various objects of the present invention are attained by the unique shift signal control system.

SHIFT SIGNAL CONTROL SYSTEM The shift signal control system which is the essential feature of the present invention includes a throttle position detecting or responsive circuit 320, an output shaft r.p.m. detecting circuit 201, a 1-2 shift point computer circuit 358, a 2-3 shift point computer circuit 363, and amplifiers 350 and 356.

The output shaft r.p.m. detecting circuit 201 includes an output shaft r.p.m. detecting means 70 and a digital-analog converter 310. The output shaft r.p.m. detecting means 70 has a structure as shown in FIGS. 13a and 13b and is composed of an r.p.m. detector 71 mounted on the transmission housing 18' and a toothed disc 72 secured integrally to the output shaft 18. The toothed disc 72 has a number of teeth of n, for example, n 32 so that the r.p.m. detector 71 detects an electrical signal S having a frequency which is n times the r.p.m. N of the output shaft 18. Thus, S n X N.

Knowing the r.p.m. N of the output shaft 18 enables the speed of the vehicle to be known. The structure of the output shaft r.p.m. detecting means 70 will be described in more detail with reference to FIGS. 13a and 13b. As seen in a side elevation in FIG. 13a, the toothed disc 72 which is secured at its center of rotation to the output shaft 18 is a discal plate of magnetic material having thirty-two equally spaced teeth formed along its circumference, and the r.p.m. detector 71 is mounted on the housing 18' at a position closely adjacent to the toothed disc 72 in a direction which is diametrically opposed to the latter. The r.p.m. detector 71 is composed of a permanent magnet 91 and a coil 92 wound around the permanent magnet 91. The permanent magnet 91 and the coil 92 are housed in a suitable casing of non-magnetic material and the casing is mounted on the transmission housing 18' so that one end of the permanent magnet 91 is disposed in close proximity to the outer periphery of the toothed disc 72. As the tooth portion of the toothed disc 72 passes through the magnetic field of the permanent magnet 91 as a result of rotation of the toothed disc 72, a variation takes place in the leakage flux of the permanent magnet 91 so that an electromotive force is produced in the coil 92. In the case of the illustrated example, one complete rotation of the toothed disc 72 produces 32 voltage pulses. As described hereinbefore, a voltage signal at an AC. voltage S is generally obtained when the toothed disc 72 having n teeth rotates at N number of revolutions per minute. The voltage signal appears across output terminals 93. It will be apparent for those skilled in the art that, in lieu of the above manner of vehicle speed detection, a small-sized generator may be mounted in coaxial relation with the driven gear operatively connected with the speedometer cable and the output from the generator may be utilized for the vehicle speed detection.

The output voltage signal S delivered from the output shaft r.p.m. detecting means 70 is supplied to the digital-analog converter 310 through a lead 311. The digital-analog converter 310 converts the A.C. signal or digital signal S into a DC. voltage signal or analog signal. The digital-analog converter 310 has a structure as shown in FIG. 14 the elements of which are the same as described in the Shirai et al. U.S. Pat. No. 3,572,168 (FIG. 9) and in the aforementioned Wakamatsu et al. application, Ser. No. 874,934. The input voltage signal S is supplied by the lead 311 to an amplifier 313 in which the amplitude of the signal is increased, and then the amplitude of the signal S is limited to a fixed value by an amplitude limiter 314. The A.C. voltage is then converted into a DC. voltage by a frequency detecting, rectifying and amplifying circuit 315, and the DC. voltage is led out by a lead 312. The voltage waveforms appearing in the circuit 310 are shown in FIGS. 15a to 150. FIG. 15a shows the voltage waveform of the signal S and the same waveform is maintained after the signal S has been amplified. FIG. 15b shows the waveform of the output from the amplitude limiter 314. FIG. 150 shows the waveform of the output En from the frequency detecting, rectifying and amplifying circuit 315, and this output En is an analog voltage which is proportional to the r.p.m. of the output shaft 18.

The throttle position responsive circuit 320 has a structure as shown in FIG. 16. The reference numeral 322 designates a multi-contact switch which is responsive to the position of the throttle valve in the carburetor, or in other words, responsive to the degree of depression of the accelerator pedal. (This switch may respond to a displacement of a member responsive to the negative pressure in the air intake pipe since the switch is a means for detecting an engine torque responsive signal.) The multi-contact switch 322 has a movable contact 323 and a plurality of stationary contacts 324, 325, 326, 327, 328 and 329. The switch 322 is so constructed that the movable contact 323 is successively released from contact with the stationary-contacts 324, 325, 326,327, 328 and 329 as the opening S 9 of the throttle valve is successively increased to S a 1 S o (2), S o (a) S 4) 5 o (s) and 5 a The movable tact 323 is grounded at one end thereof. The stationary contacts 324, 325, 326, 327 328 and 329 are connected at one end to the respective variable resistors 324, 325, 326, 327f, 328 and 329, while one end of the variable resistor 319 is grounded. The variable resistors 324 through 319 are connected at the other end in common to the lead 321. A resistor 318 is connected at one end to a lead 321, and a fixed voltage E is applied to the other end of the resistor 318.. The variable resistor 319 is so adjusted that a voltage E appears on the lead 321 when S0 S 1 due to the full opening of the throttle valve in the carburetor. Then, when the throttle valve opening is reduced to S9 in. the movable contact 323 solely engages with the stationary contact 329. The variable resistor 329 E E(6), where R, R and R are the resistances of the resistor 331, variable resistor 329 and variable resistor 319', respectively, and R ll R is the resistance given when the variable resistors 329 and 319 are connected in the circuit in parallel with each other. The variable resistor 328' is so adjusted that an output E appearing on the lead 321 in response to the throttle valve opening of 8 5 is given by E E where R is the resistance of the variable resistor 328'. Similarly, the variable resistors 327', 326', 325' and 324' are so adjusted that the outputs appearing on the lead 321 in response to the throttle valve Openings of am aw) 6(2). ou) are given y M) E E and E respectively. Thus, the voltages E E g E(3), E(q E(5), Em and E(7) appear on the lead in response to the throttle valve opening S, of S S ous) am 0(5), 0(6) and am respectively- In other words, a stepped signal voltage E (N 1, 2, 3, 4, 5, 6, 7) is delivered from the circuit 320 to the lead 321 depending on the opening of the throttle valve. The switch 322 is shown as having six stationary contacts for obtaining seven different outputs. It is apparent that the number of stationary contacts may be further increased in order to obtain a more complex stepped signal.

The 1-2 shift point computer circuit 358 includes a discriminating circuit 330 and a feedback circuit 340. The discriminating circuit 330 and the feedback circuit 340 have a structure as shown in FIG. 17. The discriminating circuit 330 includes a comparator 335 of any suitable conventional type such as one sold under the code No. upc 71 by Nippon Electric Co., Ltd. (as shown in detail in FIG. 1 1b of the copending Wakamatsu et a1. application, Ser. No. 858,300 filed Sept. l6, l969) or N727 ION supplied by Texas Instruments Co., Ltd. An input resistor 336 is connected at one end to an input terminal 335a of the comparator 335 and at the other end to the movable arm of a variable resistor 337. The variable resistor 337 is connected across the input terminals 333 and 334 of the discriminating circuit 330. A resistor 338 is connected at one end to the movable arm of a variable resistor 339 and at the other end to an input terminal 335b of the comparator 335. The variable resistor 339 is connected at one end to the input terminal 332 of the discriminating circuit 330 and is grounded at the other end. Terminals 335e, 335d and 335e of the comparator 335 are connected to the positive terminal of a power source, to ground and to the negative terminal of the power source, respectively. The feedback circuit 340 includes an NPNtransistor 341, aresistor 342 and a variable resistor 343. The

NPN transistor 341 has its emitter grounded and its base connected to the output lead 331 of the dis criminating circuit 330 through the resistor 342. The collector of the transistor 341 is connected to the fixed terminal of the variable resistor 343 and the junction point therebetween is connected to the input terminal 334 of the discriminating circuit 330. The variable contact of the variable resistor 343 is grounded.

In operation, assuming that a voltage or l appears on the output lead 331 when no signal is supplied to the input terminals 332, 333 and 334, then a base current is 

1. In an automatic transmission for an engine-driven vehicle having a torque converter coupled to a gear unit having gears and frictionally engaging means for accomplishing the selective meshing engagement of said gears in said gear unit, an automatic shift control system comprising: a hydraulic actuating circuit means including a manual fluid valve having a first position for establishing a relatively high forward driving ratio and a second position for establishing a relatively low forward driving ratio and shift valve means disposed in fluid communication passages between said manual valve and said frictionally engaging means for selectively actuating said frictionally engaging means; electrical signal generating means connected to said vehicle and including at least one signal generator for generating an electrical output signal representing at least one shift determining type of vehicle operating condition; electrical shift point computing means coupled between said generating means and shift valve means for automatically computing shift point signals representing an automatic shifting pattern for actuating said shift valve means as a function of the Output of said signal generating means; and control means for varying said automatic shifting pattern thereby varying the shift point even though said manual fluid valve is maintained in said first position whereby a suitable shift point may be manually selected as desired depending on the varying driving conditions of the vehicle.
 2. In an automatic transmission for an engine-driven vehicle having an engine throttle, said transmission being of the kind having an output shaft and a torque converter coupled to a gear unit containing gears for driving said shaft and having frictionally engaging means for accomplishing the selective meshing engagement of the gears in said gear unit, an automatic shift control system comprising: a hydraulic actuating circuit including a manual shift region setting valve and a distributing valve for distributing fluid under pressure to said frictionally engaging means for controlling said frictionally engaging means, first means connected to said throttle for generating a first signal responsive to the engine throttle position, second means connected to said transmission output shaft for generating a second signal responsive to the r.p.m. of the output shaft of said transmission, a plurality of discriminating circuit means connected to said first and second means for generating an output signal when the relation between said first and second signals satisfies a predetermined condition, switch means connected with at least one of said discriminating circuits for permitting or interrupting the delivery of the output signal from said discriminating circuit, and OR circuit means coupled to said discriminating circuits for generating an electrical output signal for triggering actuation of said frictionally engaging means when at least one of the signals from said discriminating circuits is applied thereto directly or through said switch means.
 3. In a shift control system for a vehicle transmission which includes a transmission gear assembly, engaging means coupled to said assembly for effecting gear shifting engagement of said transmission gear assembly, and shifting means coupled to said engaging means for operating said engaging means, the improvement comprising: electrical signal generator means connected to said vehicle for producing electrical output signals representative of shift determining operating conditions of the vehicle, computing circuit means connected to the output of said signal generator means for acting upon the output signals therefrom to establish a shift condition, means connected to the output of said computing circuit means for actuating said shifting means, a shift condition modification circuit connected between said computing circuit means and said actuating means for varying said shift condition when said modification circuit is energized and means coupled to said shift condition modification circuit for manually affecting energization thereof.
 4. The shift control system of claim 3 wherein said signal generating means comprises a toothed disc of magnetic material securely mounted coaxially on the output shaft of said vehicle transmission and a coil located adjacent to the outer periphery of said toothed disc the axis of said coil being located on a line radial to said disc whereby a voltage having a frequency proportional to the rotational speed of said output shaft is induced in said coil.
 5. The shift control system of claim 4 further including a digital to analog converter electrically connected between said coil and said establishing circuit.
 6. The shift control system of claim 3 wherein said signal generating means comprises a movable contact mechanically connected with the carburetor throttle of said vehicle, a plurality of fixed contacts arranged to engage with said movable contact, each of said fixed contacts being connected through a separate resistance to a source of electrical power, and a voltage tap line connected in common between said resistances and said power source wherein the movement of said carburetor throttle causes said movable contact to engage a varying number of fixed contacts and thus to vary the output voltage on said voltage tap line proportional to the setting of said carburetor throttle.
 7. The shift control system of claim 3 wherein said signal generating means comprises a toothed disc of magnetic material securely mounted coaxially on the output shaft of said vehicle transmission and a coil located adjacent to the outer periphery of said toothed disc the axis of said coil being located on a line radial to said disc whereby a voltage having a frequency proportional to the rotational speed of said output shaft is induced in said coil, and a movable contact mechanically connected with the carburetor throttle of said vehicle, a plurality of fixed contacts arranged to engage with said movable contact each of said fixed contacts connected through a separate resistance to a source of electrical power and a voltage tap line connected in common between said resistances and said power source wherein the movement of the carburetor throttle causes said movable contact to engage a varying number of said contacts and thus to vary the output voltage on said voltage tap line proportional to the carburetor throttle setting.
 8. The shift control system of claim 3 wherein said shifting means comprises a source of pressurized liquid and a hydraulic system having at least one valve for controlling the flow of liquid within said hydraulic system and at least one hydraulic operator in liquid connection with said hydraulic system and in mechanical connection with said engaging means for operating said engaging means.
 9. The shift control system of claim 8 wherein said engaging means comprises at least one clutch and said hydraulic operator comprises a servo chamber mechanically adapted to cause the engagement of said clutch.
 10. The shift control system of claim 8 wherein said engaging means comprises at least one brake band and said hydraulic operator comprises a servo chamber mechanically adapted to cause the engagement of said brake band.
 11. The shift control system of claim 3 wherein said signal generating means produces two signals and said establishing circuit comprises a comparator having first and second input leads and an output lead, one of said two signals being applied to said first input lead and the other of said two signals being applied to said first input lead, said comparator producing an output on said output lead only when said first signal exceeds said second signal.
 12. The shift control system of claim 11 further including a feedback circuit connected between said output lead of said comparator and said first input lead thereof for adding a portion of the output signal produced by said comparator to the input signal at said first input lead whereby signals on said output lead are stabilized.
 13. The shift control system of claim 12 wherein said shift modification circuit comprises a second comparator which is electrically identical to the first comparator and has electrically identical input and output leads but differs from said first comparator in that a reference signal is applied to the second input lead of said second comparator whereby said second comparator produces a different output from said first comparator and an electrical ''''or'''' gate to which the output leads of said first and second comparators are connected as inputs and from which an output lead extends which is connected to said actuating means and means causing said ''''or'''' gate to connect either said first or said second comparator to said actuating means.
 14. The shift control system of claim 13 wherein the means for energizing said shift condition modification circuit comprises a switch connected between said second comparator and said ''''or'''' gate.
 15. In an automatic transmission for an engine-driven vehicle having a torque converter coupled to a gear unit having geArs and frictionally engaging means for accomplishing the selective meshing engagement of gears in said gear unit to effect shifting between various gear ratios, an automatic shift control system comprising: hydraulic actuating means including a manually controlled fluid valve connected to said frictionally engaging means for selectively actuating said frictionally engaging means to effect said shifting in response to supplied electrical shift point signals, electrical signal generating means connected to said vehicle for being responsive to at least one gear shift determining type of vehicle operating conditions for supplying electrical output signals representative thereof, computing means connected between said signal generating means and said hydraulic actuating means for automatically computing and supplying as an output a first set of electrical shift point signals as a first function of said vehicle operating conditions corresponding to a first shift pattern suitable for a first driving environment, further means connected to said computing means for effecting a change in the output thereof to a second set of electrical shift point signals as a second function of said vehicle operating conditions corresponding to a second shift pattern suitable for a second driving environment, and manual switch means for manually activating said further means independently of said manually controlled fluid valve whereby a driver of said vehicle may manually change the system operation, from said first shift pattern to said second shift pattern upon detecting a change from said first to said second driving environment.
 16. An automatic shift control system as in claim 15 wherein said hydraulic actuating means includes electrically operated solenoid valves which are spring biased to an up-shifted position so that no electrical operating power is required during high gear operation.
 17. An automatic shift control system as in claim 16 wherein said manually controlled fluid valve effects completely manual control over said shifting between various gear ratios when said electrically operated solenoid valves are in their spring biased positions.
 18. An automatic shift control system as in claim 15 wherein: said further means comprises a second computing means connected to said signal generating means for automatically supplying second output signals as a function of at least one of said shift determining vehicle operating conditions and an OR circuit connected to both of said computing means for effectively combining said first set of electrical shift point signals with said second output signals to produce said second set of electrical shift point signals, and said manual switch means is connected to the output of said second computing means for effectively disconnecting said second output signals from said OR circuit in response to manual actuation by a driver of the vehicle. 